1. Field of the Invention
The present invention relates to electrostatic speakers in which vibrators held between opposite electrodes vibrate in response to audio signals so as to generate sounds.
The present application claims priority on Japanese Patent Application No. 2007-251158 and Japanese Patent Application No. 2008-132235, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Electrostatic speakers are constituted of opposite electrodes, which are distanced from each other with prescribed distances therebetween and which hold sheet-like vibrators (or vibrating members) having conductive properties therebetween. Due to variations of a voltage applied between opposite electrodes of an electrostatic speaker whose vibrator is supplied with a bias voltage, an electrostatic force exerted on the vibrator is varied so as to cause the displacement of the vibrator. Due to variations of the applied voltage in response to audio signals, displacements repeatedly occur in the vibrator causing vibration, thus generating reproduction waves from the vibrator in response to audio signals.
Various types of electrostatic speakers having flexibilities have been developed and disclosed in various documents such as Non-Patent Document 1 and Non-Patent Document 2.    Non-Patent Document 1: Technical Report of the Institute of Electronics, Information and Communication Engineers entitled “1-bit Wave Field Recording/Reproduction System Using Electrostatic Microphone and Loudspeaker” written by Shigeto Takeoka and five members, EA, Applied Acoustics, Institute of Electronics, Information and Communication Engineers, pp. 25-30, June of 2005 Non-Patent Document 2: <A & V Festa 2006 Report: 1-bit audio> exhibition of 1-bit distribution system using IEEE 1394: [online], Sep. 21, 2006, Phile-web editorial department: [Retrieval on Aug. 23, 2007]: Internet <http://www.phileweb.com/news/d-av/200609/21/16653.html>
Non-Patent Document 1 teaches a flexible electrostatic speaker including opposite electrodes and a vibrator, which are composed of flexible materials having the capabilities to change shapes. Non-Patent Document 2 teaches an electrostatic speaker in which electrodes are composed of flexible cloth.
Both of Non-Patent Document 1 and Non-Patent Document 2 teach edgeless flexible electrostatic speakers in which electrodes and vibrators are not restrained in shapes. Since the flexible electrostatic speaker disclosed in Non-Patent Document 1 is not restrained in shape, it can be freely bent and curved and thus changed into various shapes. However, such a non-restraint property of the electrostatic speaker causes another problem in that electrodes and vibrators may be easily deviated in positioning.